Ratchet screw driver

ABSTRACT

A ratchet screw driver is shown. The screw driver is comprised of a blade carrying shank which is intimately slidable within a sleeve housing provided in the handle. Complementary ratchet teeth are formed on a sloping mating surface of the handle and the shank. The ratchet teeth are normally maintained in a spaced disengaged position from each other by a biassing means in the handle. The ratchet teeth engage with each other when the blade is pressed downwards into the slot of the screw to be operated.

United States Patent [191 Douglas et al.

[ Aug. 6, 1974 1 RATCHET SCREW DRIVER 221 Filed: Mar. 1, 1973 21 Appl.No.: 336,937

[52] U.S. Cl. 145/76, 81/583 [51] Int. Cl B25b 15/04 [58] Field ofSearch 145/50 R, 76; 81/583 [56] References Cited UNITED STATES PATENTS20,61) 6/1858 Bond 145/76 1,017,035 2/1912 Benjamin 145/76 1,049,6501/1913 Benjamin 145/76 1,643,860 9/1927 Shedd l 81/583 2,667,801 2/1954Eaves 81/583 3,272,246 9/1966 Bohnet 145/76 131,309 4/1951 Swcdcn 145/76Primary ExaminerAl Lawrence Smith Assistant ExaminerJ. T. ZatargaAttorney, Agent, or Firm-David W. Wong 57] ABSTRACT A ratchet screwdriver is shown. The screw driver is comprised of a blade carrying shankwhich is intimately slidable within a sleeve housing provided in thehandle. Complementary ratchet teeth are formed on a sloping matingsurface of the handle and the shank. 'lhc ratchet teeth are normallymaintained in a spaced disengaged position from each other by a biassingmeans in the handle. The ratchet teeth engage with each other when theblade is pressed downwards into the slot of the screw to be operated.

6 Claims, 3 Drawing Figures PAIENIEW 3.827. 410

FIG. 3

RATCHET SCREW DRIVER This invention relates to a screw driver and moreparticularly relates to a ratchet screw driver in which the blade is notfixedly mounted on the handle.

In using a fixed blade screw driver, it is necessary to disengage thescrew driver from the screw after each half turn so that the operatorcan reposition his arm for the next half turn. The operations requirethe disengaging and re-engaging of the blade of the screw driver withthe slot of the screw in each half turn. Ratchet screw drivers aredesigned to overcome such drawback. Ratchet screw drivers haveheretofore been known in which the blade is not fixedly mounted on thehandle. In one kind of ratchet screw driver, the blade is mounted to thehandle through a coupling section in whicha complicated ratchetarrangement is incorporated. The ratchet arrangement can be operated sothat the blade is only engaged to the handle when the handle is turnedin one selected direction. This facilitates the tightening or looseningof screws without having to lift the screw driver out of engagement withthe screw and thus enhances the efficiency of the operation. However,the ratchet arrangement in this kind of screw driver is complicated instructure and is expensive to fabricate; yet, despite the high cost ofmaking such screw drivers, the ratchet arrangement tends to break downeasily even under normal use.

Another kind of ratchet screw driver consists of a blade carrying shankmovably mounted to the handle and complementary ratchet teeth are formedon the handle and the shank, which can engage with each other when thescrew driver is pressed down by the axial force in use to engage thescrew. Many of this kind of ratchet screw drivers are unstable in theirconstruction and are ineffective to operate. The main drawback in thiskind of ratchet screw driver is that the mounting means between thehandles and the shank tend to fail under the turning stresses.

In US. Pat. No. 572,800 issued to H. F. Henry on Dec. 8, 1896, a ratchetscrew driver of the latter type is shown. The screw driver thereinincludes a blade carrying shank rotatably mounted to the front end of ahandle by a mounting cap. The rear end of the shank and the front end ofthe handle enclosed within the cap have complementary ratchet teethformed therein. A biassing spring is placed between the handle and theshank so that they are normally disengaged. When the screw driver ispressed down during use, the ratchet teeth on the handle and the shankare engaged together to transmit the turning movement to the screw. Inthis structure, only a short portion of the shank is enclosed within theretaining cap, which breaks easily due to the bending moment exerted atthe joint by the relatively long blade. Furthermore, the ratchet teethmust be small in dimension in order to be formed on rear end of theshank and on the front end of the handle enclosed within the mountingcap. Such fine ratchet teeth are easily worn down due to the extremeshearing stresses thereon during the turning operation of the screwdriver.

The principal object of the present invention is to provide a ratchetscrew driver which has a ratchet structure that can withstandconsiderable turning stresses during use.

Another object of the present invention is to provide a ratchet screwdriver in which the shank can withstan considerable bending force. i

Still another object of the present invention is to provide a ratchetscrew driver in which a simple but strong rigid teeth structure isprovided to transmit the turning force from the handle to the blade.

A further object of the present invention is to provide a ratchet screwdriver which is easily fabricated or dismounted for replacement orrepair.

According to the present invention, the screw driver comprises a handlehaving a hollow cylindrical center which is separated by an abutmentmeans disposed therein into a front sleeve housing and a rear sleevehousing; an opening formed in the abutment means to communicate betweenthe front sleeve housing and the rear sleeve housing; a plurality ofratchet teeth formed around the front end of the front sleeve housing; ablade carrying shank slidably engageable within the front sleevehousing; the shank having a rear portion extensible through the openingin the abutment means into the rear sleeve housing; a plurality ofcomplementary ratchet teeth formed on the shank and dimensionallycomplementary to the ratchet teeth formed around the front end of thefront sleeve housing; and biassing means disposed over the rear portionof the shank within the front sleeve housing and co-acting with theabutment means to maintain the ratchet teeth and the complementaryratchet teeth normally in a spaced disengaged position.

This and other objects of the invention, together with its advantageswill be more apparent from the following description and drawings whichillustrate a specific embodiment by way of example and in which:

FIG. I is an exploded perspective view showing the components of theratchet screw driver according to the present invention;

FIG. 2 is a cross-sectional side elevation of the screw driver showingthe relationship between the elements in assembly;

FIG. 3 is a fragmentary side elevation showing the relationship betweencomponents during use.

Referring now to the drawings in which like reference numerals indicatelike parts, the handle 10 has a hollow cylindrical center such as acircular bore 12 having a uniform diameter throughout its length. Anabutment means 13 is provided in the bore to divide it into a frontsleeve housing 14 and a rear sleeve housing 15. The abutment means 13may consist of at least two protrusions formed on the wall or a collarhaving a center opening 17 slightly smaller in diameter than the centerbore 12. The front sleeve housing 14 communicates with the rear sleevehousing 15 through the opening 17. The handle 10 may be of aconventional size and configuration which can fit comfortably in thepalm of the user, and it may be made of plastics such as polypropyleneby molding. A plurality of ratchet teeth 18 are formed in the front edgeportion of the front sleeve housing. The front edge portion preferablyhas a convergently sloping face slanting downwardly and inwardly towardsthe center axisof the housing as best shown in FIG. 2, so that itappears as a circular depression in the front end of the handle withradial ratchet teeth formed on the slanted side wall of the depression.For example, the handle may have a front edge portion having a 1 inchdiameter with a sleeve housing of about /2 inch in diameter. The ratchetteeth have a teeth angle of about 30 to 60 and the sloping surface hasabout a 1-to-2 slope (i.e., a /8 inch angle fall).

The shank consists of a cylindrical main body portion 21 having adiameter slightly smaller than the diameter of the front sleeve housingbut larger than the diameter of the center openings 17 of the collar 13such that the cylindrical body portion 21 may be intimately slidablewithin the front sleeve housing with little clearance between them. Forthe example shown above, the clearance preferably should not be morethan 1/16 inch in order to eliminate any undesirable rocking movement ofthe shank within the front sleeve housing.

A smaller rear portion 23 is formed in the rear of the shank 20. Thediameter of the rear portion 23 is slightly smaller than the centeropening 17 of the collar 13. When the body portion 21 is fully insertedin the front sleeve housing 14, the rear portion 23 can extend into therear sleeve housing through the opening 17.

The front portion 25 of the shank is dimensioned and configuredcomplementarily to the front portion of the handle 10. A plurality ofratchet teeth 26 are formed on a bevelled mating surface as best shownin FIG. 1. The mating surface slopes upwardly towards the body portion21. The slope and the dimension of the ratchet teeth 26 arecomplementary to that of the ratchet teeth 18 formed on the slopingfront edge portion of the front sleeve housing. Thus, the shank may becoupled with the handle as shown in FIG. 3 in which the ratchet teeth 18and 26 are fully engaged with each other and the front portion 25 of theshank becomes integral with the front portion of the handle; in thismanner, the end portion of the rear portion 23 is extending through theopening 17 of the collar into the rear sleeve housing.

The blade 28 is fixedly mounted in the shank during the molding of thelatter in the conventional manner with plastics. Commonly, a portion ofthe blade molded within the shank is stamped to provide at least twokeys 29 so as to transmit the turning moment directly during use fromthe handle to the blade.

The shank is mounted on the handle by a screw 30 with a washer 31provided through the rear sleeve housing 15. The screw 30 is fastened toa threaded opening 29 formed at the end of the rear end portion 23 ofthe shank. The washer is slightly larger than the opening 17, so thatonce mounted, the shank cannot be retracted from the front sleevehousing.

The total length of the main body portion 21 together with the rearportion 23 of the shank is longer than the length of the front sleevehousing. Thus, when the shank is mounted with the washer 31 abutting thecollar 13, the ratchet teeth 18 and 26 are not engaged with each other.A coil spring 35 is fitted over the rear end portion of the shank tobias the shank such that the ratchet teeth 18 and 26 are normallydisengaged with each other and are disposed in a spaced relation witheach other. The coil spring 35 preferably has an inside diameterslightly larger than the rear end portion 23 of the shank and an outsidediameter slightly smaller than the diameter of the front sleeve housingin order that it is freely compressible or extensible axially within thefront sleeve housing to provide an effective biassing action for theshank.

During use, when the blade is pressed downward to engage the slot of thescrew, the shank is forced upwards by the axial force until the ratchetteeth 18 and 26 are fully engaged with each other. As shown in H6. 3,the rear end portion 23 of the shank extends into the rear sleevehousing 15 and the coil spring 35 is being compressed due to theshortening of the rear end portion 23 in the front sleeve housing.

The turning moment of the handle by hand is transmitted to the bladethrough the fully engaged ratchet teeth 18 and 26. When it is necessaryfor the operator to return the hand or arm to a fresh position for thenext turning movement, the axial pressure on the handle is relaxed; thebiassing coil spring 35 urges the shank 20 downwards until the washer 31abuts the collar 13 and the ratchet teeth 18 and 26 become disengagedand are spaced from each other. The biassing coil spring 35 alsomaintains the blade in engagement with the slot of the screw during theabove operation. The handle may then be turned relative to the shank toreturn the hand or arm of the operator to the initial position. In thismanner, the screw can be tightened or loosened effectively withouthaving to lift the blade of the screw driver out of engagement with theslot of the screw after each half turn action.

It can be appreciated that the bevelled surfaces of the ratchet teeth 18and 26 enhance the engagement and the transmission of force between thehandle and the shank due to the increase in surface contact between theratchet teeth. The bevelled ratchet teeth 26 also are coupled intimatelyto the depression formed by the bevelled ratchet teeth 18 and it is verydifficult to displace the ratchet teeth 26 from the circular depression.Additionally, due to the complementary dimension between the frontsleeve housing and the shank, they are coupled together integrallyduring use and therefore can withstand extremely high bending stresses.

While illustrative forms of the device in accordance with the inventionhave been described and shown herein, it will be understood that numeralchanges may be made without deparing from the general principles andscope of the invention.

What we claim as new and desire to protect by letters Patent of theUnited States is:

1. A screw driver comprising a tubular handle having a longitudinalcircular center bore of a uniform diameter, a collar formed in saidcenter bore and separating said center bore into a front sleeve housingand a rear sleeve housing, said collar having an opening smaller thanthe diameter of said centre bore, a depression formed at the front endof said front sleeve housing, said depression having a slanting sidewall convergently sloping inwardly towards the axis of said center bore,a plurality of ratchet teeth formed on said slanting side wall, anelongated cylindrical shank having three integral portions thereincomprising a main body portion, a smaller rear portion and a largerfront portion, the diameter of said rear portion being slightly smallerthan said opening of said collar, said main body portion being slidablyand intimately receivable in said front sleeve housing until the endportion of said rear portion extends through said collar into said rearsleeve housing, the diameter of said main body portion being slightlyless than the diameter of said center bore of said front sleeve housing,the main body portion extending into said front sleeve housing aneffective distance to prevent rocking movement between said shank andhousing, the diameter of said rear portion being less than that of themain body portion thereby forming a shoulder where the rear portionmeets the main body portion, a blade being mounted on said front portionand extending outwardly of the center of the front end therefrom, theback wall of said front portion having a bevelled surface which has aplurality of complementary ratchet teeth formed thereon, saidcomplementary ratchet teeth being operatively engageable with saidratchet teeth formed at the front end of said front sleeve housing, aspiral spring having an outside diameter equal to the diameter of saidmain body portion and an inside diameter slightly larger than said rearend portion, said spiral spring being slidably disposed about said rearportion and co-acting between said collar and said shoulder entirelywithin said front sleeve housing to bias said shank such that saidcomplementary ratchet teeth and said ratchet teeth are normally justdisengaged and spaced from one another, a mounting means fastened at theend of said rear portion through said rear sleeve housing to preventsaid shank from being retrieved from said handle.

2. A screw driver according to claim 1 in which the mounting meanscomprises a screw fastened to the end of said rear portion through saidrear sleeve housing, said screw carrying thereon a washer having adiameter smaller than the diameter of saidcenter bore and larger thanthe diameter of the opening of said collar so as to prevent said shankfrom being withdrawn from said front sleeve housing.

3. A screw driver according to claim 2 in which said bevelled surface onsaid shank and said slanting side wall in said depression have a l-to-2slope and said ratchet teeth and complementary ratchet teeth have ateeth angle of about 30 to 60.

4. A screw driver according to claim 3 in which the total length of themain body portion and the length of the rear portion of the shank arelonger than the length of the front sleeve housing.

5. A screw driver according to claim 4 in which the clearance betweenthe main body portion of the shank and the front sleeve housing is lessthan 1/16 of an inch.

6. A screw driver according to claim 5 wherein said complementaryratchet teeth formed on said shank are dimensioned and configuredcomplementarily to said ratchet teeth formed in said front end of saidfront sleeve housing.

1. A screw driver comprising a tubular handle having a longitudinalcircular center bore of a uniform diameter, a collar formed in saidcenter bore and separating said center bore into a front sleeve housingand a rear sleeve housing, said collar having an opening smaller thanthe diameter of said centre bore, a depression formed at the front endof said front sleeve housing, said depression having a slanting sidewall convergently sloping inwardly towards the axis of said center bore,a plurality of ratchet teeth formed on said slanting side wall, anelongated cylindrical shank having three integral portions thereincomprising a main body portion, a smaller rear portion and a largerfront portion, the diameter of said rear portion being slightly smallerthan said opening of said collar, said main body portion being slidablyand intimately receivable in said front sleeve housing until the endportion of said rear portion extends through said collar into said rearsleeve housing, the diameter of said main body portion being slightlyless than the diameter of said center bore of said front sleeve housing,the main body portion extending into said front sleeve housing aneffective distance to prevent rocking movement between said shank andhousing, the diameter of said rear portion being less than that of themain body portion thereby forming a shoulder where the rear portionmeets the main body portion, a blade being mounted on said front portionand extending outwardly of the center of the front end therefrom, theback wall of said front portion having a bevelled surface which has aplurality of complementary ratchet teeth formed thereon, saidcomplementary ratchet teeth being operatively engageable with saidratchet teeth formed at the front end of said front sleeve housing, aspiral spring having an outside diameter equal to the diameter of saidmain body portion and an inside diameter slightly larger than said rearend portion, said spiral spring being slidably disposed about said rearportion and co-acting between said collar and said shoulder entirelywithin said front sleeve housing to bias said shank such that saidcomplementary ratchet teeth and said ratchet teeth are normally justdisengaged and spaced from one another, a mounting means fastened at theend of said rear portion through said rear sleeve housing to preventsaid shank from being retrieved from said handle.
 2. A screw driveraccording to claim 1 in whIch the mounting means comprises a screwfastened to the end of said rear portion through said rear sleevehousing, said screw carrying thereon a washer having a diameter smallerthan the diameter of said center bore and larger than the diameter ofthe opening of said collar so as to prevent said shank from beingwithdrawn from said front sleeve housing.
 3. A screw driver according toclaim 2 in which said bevelled surface on said shank and said slantingside wall in said depression have a 1-to-2 slope and said ratchet teethand complementary ratchet teeth have a teeth angle of about 30* to 60*.4. A screw driver according to claim 3 in which the total length of themain body portion and the length of the rear portion of the shank arelonger than the length of the front sleeve housing.
 5. A screw driveraccording to claim 4 in which the clearance between the main bodyportion of the shank and the front sleeve housing is less than 1/16 ofan inch.
 6. A screw driver according to claim 5 wherein saidcomplementary ratchet teeth formed on said shank are dimensioned andconfigured complementarily to said ratchet teeth formed in said frontend of said front sleeve housing.